As environmental problems becomes increasingly serious in recent years, renewable power sources such as solar cells and wind power generators that are rapidly being put into use are considered to be an effective means for achieving lower carbon emissions and solving the problem of energy resources. However, these types of renewable power sources experience large fluctuations in output. As a result, from the standpoint of electrical quality, an adjustment means is indispensable for offsetting the fluctuations in output of the renewable power sources. Thermal power generators, which feature rapid response speed, are currently the chief means used as such adjustment means. Thus, a dilemma may arise in which, as renewable electric power sources are increased, the number of thermal electric power generators that are not environmentally friendly need to be increased as adjustment means that adjusts large output fluctuations of the renewable electric power sources. Obtaining a powerful adjustment means to take the place of thermal power generators is therefore a major issue. As such an adjustment means, the introduction of high-capacity storage batteries (such as sodium sulfur batteries) is effective, but from the standpoint of installation and operating costs, the introduction of high-capacity storage batteries is considered to face extremely high obstacles.
Great strides are being made in research relating to V2G (Vehicle-to-Grid) technology that, by effecting multiple linkage and operation, employs the storage batteries that are mounted in vehicles that run on electricity (hereinbelow referred to as EV (Electric Vehicles) that include hybrid electric vehicles that are equipped with storage batteries together with another motive power source) and that are expected to rapidly come into widespread use, similar to renewable power sources and the chargers to which these storage batteries are connected as virtual high-capacity storage batteries for electric power system stabilization. The V2G proposal itself dates to the 1980s, and research reports estimating the extent of the macro stabilization effect over an entire electric power system network have been issued continuously. In the past few years, the reports have come to focus on technology relating to real-time control, and moreover, micro control methods, i.e., individual charging and discharging of multiple EVs for the construction of an actual system.
For example, Non-Patent Document 1 describes a charging/discharging control method for implementing optimum scheduling by Particle Swarm Optimization (PSO), which is inspired by the movement of a school of fish, by setting EV operation models, distribution network models, and time-variation models of the price of electric power.
Patent Document 1 describes the configuration of an EV charging planning device and refers to optimum charging scheduling that uses a genetic algorithm.
A case that assumes not only the charging of an EV but also the discharging from the EV to the distribution network (electric power system side) is typically referred to as V2G. However, a case that assumes only charging of an EV may be referred to as G2V to distinguish from V2G. G2V is assumed to decrease the load upon the internal storage batteries of an EV in proportion to the decrease of the number of charge/discharge cycles.